Stewart has also represented Australia in five Tests, NSW in five State of Origin clashes and played three games for Country Origin and once for the Prime Minister's XIII against Papua New Guinea in 2009.
Rabbitohs coach Michael Maguire is delighted Souths have secured his services.
"Glenn is one of the linchpins to the extended success the Sea Eagles have had over the past decade and he will bring a lot to our club," Maguire said.
"Glenn has achieved a lot throughout his time in the game and the experience that he has at the highest levels on the biggest stage, as well as his leadership qualities, will be invaluable to the young players we have coming through in our squad.
"He's a tough player in attack and defence that can ball-play as well, and we're looking forward to adding him to our squad during the next pre-season."
Stewart says he's excited about the new beginning that lies ahead.
"I've really enjoyed the times I've had at Manly over the past 12 seasons but circumstances at the club have led to me moving on at the end of this year," Stewart said.
"I'm glad to have this sorted out early in the season so that I can now concentrate on finishing off the job I need to do for Manly this year."
Stewart's brother Brett remains under contract with Manly but the star fullback has said he will never play against Glenn, leaving the Sea Eagles under pressure to retain the prolific try-scorer.
- AAP
